I'm not quite sure what you're asking. If you want to know which F seats on a CRJ are bulkhead, it would be any F seat without another seat in front of it.
If you're asking about the seats behind the F cabin, no DL CRJs have a hard wall at the bulkhead, so they all have lots of leg room. If you get B, there is no seat in front of you and everyone will hit you with their luggage while boarding.